The demonstration of a serum antibody for the basement membrane of epithelial tissue has stimulated considerable speculation as well as solid research. Evidence for pemphigoid being an immunologic disease includes the following: (1) patients possess a serum IgG antibody for their own skin basement membrane, (2) this antibody is capable of binding complement, (3) both antibody and complement are found at the exact site of the pathologic change of pemphigoid, (4) polymorphonuclear leukocytes make up the major portion of the inflammatory infiltrate in this disease, and (5) the disease has a chronic clinical course. Evidence against pemphigoid being an immunologic disease is (1) the inability to transfer the disease passively, and (2) that disease activity is not consistently correlated with serum antibody levels.